Certificate of correction



E. THORPE Feb. 9, 1960 SPINNERET Filed June 12, 1953 INVENTOR ERNESTTHORPE ATTORNEY United S t s P r SPINNERET Ernest Thorpe, Newport, Del.,assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., 2corporation of Delaware Application June 12, 1953, Serial No. 361,130

5 Claims. (Cl. 18-8) This invention relates to spinnerets and morespecifically to the novel orifices formed therein.

Revolutionary new methods for spinning synthetic textile filaments haverecently been discovered which involve interfacial polymerization. Inaccordance with these methods filament formation and polymer formationare accomplished simultaneously when one of a pair of fastreactingcondensation polymer-forming intermediates is extruded as a shapedstream into a bath containing the complementary intermediate. Reactionthen takes place between the intermediates at the interface between bathand stream to form a filamentary polymer in situ. Difficulty has beenexperienced in attempting to maintain continuous operation when usingconventional spinnerets, which has been traced, at least in part, tojetting of the filamentary streams because of the low viscosity of thesolutions. Viscose-type spinnerets, which have been used verysuccessfully for years in the coagulation spinning of cellulose xanthatesolution, which is of relatively great viscosity, do not givesatisfactory results in this new interfacial polymerization-spinningprocess.

It is therefore an object of this invention to provide a satisfactoryspinneret for use in interfacial polymerization-spinning. Another objectof this invention is to provide a novel spinneret. Other objects willbecome apparent from the description that follows and the claims.

The objects of this invention are accomplished by preparing aviscose-type spinneret in the usual way and then subjecting the facethereof to a special polishing treatment whereby the shoulders of theorifices are rounded and the areas around the orifices are slightlyrecessed, as described in detail hereinafter. Spinnerets prepared inthis way are satisfactorily adapted for use in interfacialpolymerization-spinning, and continuous spinning of good, uniformmultifilament yarn over long periods of time becomes possible throughthe use of these novel spinnerets.

In the drawings, which illustrate a preferred embodiment of theinvention,

Figure 1 is a plan view drawn from a microinterferometer photograph of asingle hole of a spinneret prepared in accordance with this invention(about 200 diameters enlargement) Figure 2 is a sectional elevationcorresponding to Figure l, and

Figure 3 is a normal size view of a typical spinneret.

Spinnerets of the prior art have been made of a variety of materialsincluding noble metal alloys, such as platinum and gold or platinum andrhodium, base metal alloys, such as stainless steel, and non-metallicmaterials, such as glass or plastic. Any of these may be used inaccordance with the present invention, but tantalum has been foundpreferable in spinnerets for use in interfacial polymerization-spinning.A tantalum spinneret such as one of the forms common to the viscose art,is mounted in a conventionalviscose-type spinneret polisher which turnsthe spinneret during polishing so that it is polished in all directionsparallel to the face. The spinneret surice face is shaped by polishingfor a sufiiciently long time with chrome rouge (Grade T-9l manufacturedby S. A. Day Manufacturing Company is suitable), used with a lightmineral oil on a felt wheel. Preferably this treatment is followed bypolishing with a dispersion of aluminum oxide grain powder, such as gritNo, l000-W, in monopole oil and water on a jewelers cloth wheel toremove scratches and put a finer polish on the spinneret surfaces.

The treatment with the coarser abrasive is continued for sufficient timeto round off the orifice shoulders as shown in Figures 1 and 2 to adepth of at least 0.05 times the orifice diameter. The area around anorifice of a suitably processed spinneret appeared as shown in Figure 1when photographed with a microinterferometer at a magnification of 200diameters. The generally circular lines surrounding the orifice are thecontour lines projected on the surface with this instrument, and eachsuccessive line indicates a difference in depth of 10 millionths of aninch. The orifice diameter was 0.003 inch, and the diameter of thedepressed area within the outermost, generally circular, contour line 10was about 0.014 inch. The spacing of the contour lines indicates thatthe slope of the depressed area, which was gradual near the outside,became increasingly steep and reached a depth of about 0.0004 inch atthe edge 12 of the orifice.

Figure 2 was drawn from Figure 1 by projecting points of intersection ofthe contour lines with a diameter. Only one-tenth the number of contourlines shown in Figure 1 can be shown in Figure 2, because of crowding ofthe lines, so the distance between the lines represents 0.0001 inch onthe actual spinneret. The shape of the depressed area shown is typicalof suitable spinnerets prepared in accordance with this invention. Theshoulders of the orifice have been polished to an approximatelyparabolic curvature. The precise amount of dishing or cupping of thespinneret face may be varied as required and will depend upon thediameter of the orifice, the particular use for which intended, and thespacing of orifices in a multiple hole spinneret, such as that shown inFigure 3. Spinnerets, depending upon the use, may have any number oforifices from 1 to 10, 20, 50 or or more.

For interfacial polymerization-spinning, spinnerets should have theorifice shoulders rounded to a maximum depth at the orifice edge 12 ofabout 0.07 to 0.2 times the diameter of the orifice, the maximumdiameter of the depression within the more or less circular boundary 10should be about 3 to 6 times the diameter of the orifice, and the shapeof the depression should approximate the shape shown in Figure 2. Thisshape may be expressed matematically by the parabolic equation y =kx,where x is the horizontal distance from the edge of the orifice of apoint on the curved surface, y is the elevation of the point above themaximum depth of the depression at 12, and k is a constant whose valueis readily determined by substituting values of x and y, e.g., for thespinneret illustrated k is about 0.00003. Within these generalspecifications the precise dimensions for optimum conditions will dependupon the material extruded, the desired rate of spinning and thespinneret materal.

Other methods for producing the depressed areas around the orifices inthe spinneret face may be used provided the method produces the desiredrounded orifice shoulders as described herein. Variations include theconventional grinding, polishing or bufilng techniques of the art, butemploying suitable abrasives and/or continuing the treatment for anunusually long time to produce the required result with the particularspinneret material.

Since many dilferent embodiments of the invention Patented Feb. 9, 19.60

9,923,969 i v H f may be made without departing from the spirit andscope thereof, it is to be understood that the invention is not limitedby the specific illustrations except to the extent defined in thefollowing claims.

What is claimed is:

a 1. In a spinneret assembly for spinning textile filaments theimprovement comprising in combination a spinneret having orificeshoulders at the face of the spinneret rounded to an approximatelyparabolic curvature extending to a depth at the edge of the orifice offrom about 0.05 to about 0.2 times the orifice diameter,

2. In a spinneret assembly for spinning textile filaments theimprovement comprising in combination a spinneret having orificeshoulders at the face of the spinneret rounded to a depth at the edge ofthe orifice of from about 0.07 to about 0.2 times the diameter of theorifice.

3. In a spinneret assembly for spinning textile filaments theimprovement comprising in combination a spinneret having orificeshoulders rounded to an approximately parabolic curvature reaching adepth at the edge of the orifice of from about 0.07 to 0.2 times thediameter of the orifice.

- 4. In a spinneret assembly for spinning textile filaments theimprovement comprising in combination a spinneret having an orificesurrounded by a recessed area at the face of the spinneret of about 3 to6 times the diameter of the orifice and sloping to a depth at the edgeof the orifice of from about 0.07 to 0.2 times the diameter of theorifice.

5. In a spinneret assembly for spinning textile filaments 4 theimprovement comprising in combination a spinner'et having orificeshoulders at the face of the spinneret rounded to approximate aparabolic curvature of the form y =kx where x is the perpendiculardistance from the 5 edge of the orifice of a point on the curvedsurface, y

is the elevation of the point above the maximum depth of the curve atthe orifice edge and has a value of from about 0.07 to 0.2 times thediameter of the orifice, k is 3 a constant, and the diameter of thecurved surfare is from 10 about 3 to 6 times the diameter of theorifice.

References Cited in the file of this patent UNITED STATES PATENTS1,604,216 Brainin Oct. 26, 1926 1,654,936 Jones Jan. 3, 1928 2,291,873Brubaker Aug. 4, 1942 2,360,680 Holzmann Oct, 17, 1944 2,514,189 Spenceret a1. July 4, 1950 20 2,553,692 Webb May 22, 1951 2,566,283 Dowson Aug.28, 1951 2,660,302 Gersman Nov. 24, 1953 2,677,148 Webb May 4, 19542,750,034 Gersman June 12, 1956 25 FOREIGN PATENTS 58,189 SwitzerlandDec. 19, 1911 f OTHER REFERENCES UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No 2,923,969 February 9, 1960 Ernest Thorpe ppearsin the printed specification It is hereby certified that error aorrection and that the said Letters of the above numbered patentrequiring 0 Patent should read as corrected below.

Column 3, line 19, after "spinneret" insert having an orifice surroundedby a recessed area at the face of the spinneret and Signed and sealedthis 15th day of November 1960.

(SEAL) Jittest:

KARL He AXLINE Attesting Oflicer ROBERT C. WATSON Commissioner'bfPatents

